Germination

Warm soil stimulates tomato seeds to germinate faster than cooler earth. In fact, Organic Gardening reports that a 10-degree window between 75 and 85 degrees Fahrenheit is the best temperature range for successful germination in just one week. In contrast, soil temperatures that drop below 60 degrees Fahrenheit greatly increase the germination time. Two weeks may need to pass at this cool temperature before the seed coat fractures for root growth.

Seedlings

Unlike the high temperatures required of germination, soil temperatures for seedlings must be lower to encourage leaf growth. New foliage cannot take the stress of hot or cold soil temperatures; seedlings may wilt and die quickly since they do not have the vast foliage for photosynthesis and energy production to fight against the stress. Soil temperatures at approximately 70 degrees Fahrenheit are optimal for seedling cultivation. Since outside temperatures swing excessively between day and night, most gardeners prefer to grow their tomato seedlings indoors for the best soil temperature control.

High Temperatures

Tomato plants are known as warm-season crops; temperatures at about 86 degrees Fahrenheit are optimal for plant and fruit growth during the spring and summer months on a south-facing area of your property. But soil temperatures that exceed 95 degrees Fahrenheit by approximately 10 a.m. are too extreme for even the established tomato plant, states Colorado State University Extension. If the plant has flowered, the blossoms drop at this high temperature. As a result, pollination activities become difficult for pollinators looking for the open blooms.

Low Temperatures

Cool soil temperatures affect the tomato plant negatively, especially if they persist for more than a week. Temperatures dipping below 55 degrees Fahrenheit stops both pollen production and overall plant growth. As a result, you see visible stunting to both foliage and fruits, if the plant produces fruits at all. Fruits that do find a way to grow to full development do not have the typical firm feeling in your hand. Tomatoes feel spongy and their taste is compromised.

About the Author

Writing professionally since 2010, Amy Rodriguez cultivates successful cacti, succulents, bulbs, carnivorous plants and orchids at home. With an electronics degree and more than 10 years of experience, she applies her love of gadgets to the gardening world as she continues her education through college classes and gardening activities.

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